The invention is related to field electromagnetic materials, and in particular to a bulk gyrotropic metamaterial with large Faraday-like rotation in the absence of an external magnetic bias.
Electromagnetic materials lacking local time-reversal symmetry, such as gyrotropic materials, are of keen interest and importance both scientifically and technologically. Scientifically, topologically-nontrivial phenomena, such as photonic chiral edge states, allow for reflection-free transport even in the presence of large disorder. Technologically, nonreciprocal photonic devices, such as optical isolators and circulators, play critical roles in optical communication and computing technologies due to their ability to eliminate cross-talk and feedback.
Nevertheless, most known natural materials that lack local time-reversal symmetry require strong external fields and function only in a limited range of the electromagnetic spectrum. Among natural mechanisms leading to gyrotropy, ferromagnetic resonance (1) is one of the strongest gyrotropic effects requiring a bias magnetic field at sub-Tesla levels, but is limited to the GHz frequency range. Magnetized plasma (2) and Zeeman splitting of optical dipole transitions do provide gyrotropy at optical frequencies, but at a very weak level even with a biasing field of several Tesla. These constraints, together with associated large absorption, have so far prevented large-scale application of nonreciprocal photonic systems. However, the recent advent of photonic crystals and metamaterials enabled synthesis of artificial composite materials, possessing previously nonexistent electromagnetic properties, such as negative indices of refraction.